In today’s fast-paced environment, manufacturers are under increasing pressure to deliver on time while still being flexible enough to handle unexpected changes. They need to operate within shorter lead times and satisfy greater and increasing customer demands. To achieve this, they require the capability to schedule production smarter and more dynamically, while hoping for as little downtime as possible. In addition, they need the ability to monitor what is happening on the production floor in real-time to enable real-time decisions.
Although ‘better scheduling’ might sound like a simple answer, the reality is that this exercise of knowing which order to place on what line and in which sequence is mostly performed by singular individuals in the company who, mostly under pressure, base their scheduling on experience and gut feel. Should that person be on leave or off sick, then … well, fingers crossed that it does not happen.
Optimising discrete manufacturing
In the discrete manufacturing environment, a tool change or the reconfiguration of a production line is a major cause of production loss. Planners continuously try to compensate for this, however, in most cases, it is not the only constraint they need to consider. Although changing tools or the configuration of a production line is a necessary exercise, it can easily take hours, if not days, to ensure that the machine or line is ready to run the next order. Unfortunately, time spent on tool change or line configuration is not something that can be eliminated. However, it is possible to optimise and reduce the time it takes. Many companies use a combination of SMED (single minute exchange of dies) principles in combination with a scheduling solution to achieve this optimisation. Modern scheduling tools go a long way to assist production personnel achieve less downtime, more throughput and happier customers.
A practical example
Let us look at the example of manufacturing items of different colours on the same line or machine. A large part of the tool change exercise is to ensure that the equipment is clean and fit for use for the next product. If you are manufacturing a black item and the next order requires a light one, then a full machine cleaning, possibly combined with a complete die change-out will be required, or otherwise, many items may have to be discarded, as the black colour will take significant time to work itself out of the machine. If, however, another order lower down in the queue is for dark blue items, it may be a viable option to move this order up in the queue as it will require less cleaning as the black pigment will only shade the blue a little darker for the first number of units produced.
Other examples include the bottling of soft drinks, where orders for lighter colour drinks can be scheduled first followed by gradually darker shade colours, which reduces the time spent on CIP (cleaning in progress) and utility usage. When cutting large coils of material, the number of knives that need to be changed between orders can be drastically reduced if orders of similar or gradually changing sizes are scheduled together. Where production lines for fast-moving, short-cycle orders consist of mostly manual labour, it may be possible to schedule products requiring the same number of people on the same line, reducing under-or-over resourcing of production lines.
The above sounds simple and logical, however most companies have multiple lines and machines operating simultaneously, processing a large amount of frequently changing orders and priorities continuously. In this scenario, the alternative and possible sequences can quickly become overwhelming, if not impossible, for one person to comprehend, correlate and re-schedule – no matter how smart the Excel spreadsheet is.
Scheduling algorithms
Modern scheduling software tools have been specifically developed to meet this need for small, medium and large enterprises. By using advanced algorithms that balance demand and capacity to generate achievable production schedules, modern scheduling software provides an interactive, multi-constraint scheduling system. The availability of human resources, equipment capacity, tooling and materials availability, as well as product variables such as colour, thickness and line configuration, for instance, are all considered in scheduling rules. Orders can be scheduled quickly by using intelligent built-in business rules and the planner can also manually interact with the schedule to make changes based on their experience, changing priorities, or unexpected supply constraints.
By defining specific schedule optimisation rules, the planner will be able to dynamically calculate the preferred or optimal sequence to minimise changeover or line configuration times. Such scheduling systems can be customised and configured as needed and can be used as a standalone system or integrated with enterprise and production software, such as MES and ERP systems.
Companies that implemented dedicated production scheduling software realised benefits such as:
• The optimisation of production operations.
• Significant reduction of non-value-added activities such as setup and tooling time.
• Reduction of late deliveries due to manufacturing delays.
• Lower production costs due to less costly downtime.
Although production scheduling can be a frightening task, modern purpose-built scheduling software will ensure that you get a good night’s rest – even if the planner decides to sleep in!
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